1. Field of the Invention
The present invention relates to an athletic shoe used at the time of going out, jogging and playing sports in daily life.
2. Description of Prior Arts
Midsole is a member arranged on an outer sole and absorbs a shock at the time of landing one's foot. For that purpose, the midsole is composed of a material effective in shock absorption and resilience such as EVA (ethylene-vinyl acetate copolymer) sponge (foam). To achieve the characteristics of EVA, hardness of the EVA sponge is usually set to a relatively small value of 40.degree. to 60.degree.. As a result, increase of pronation is accelerated in some cases.
Generally, during running, a foot landed from lateral side (outside) of a heel becomes parallel to a road surface and subsequently the heel of the foot inclines a little toward medial side (inside). This inclination of heel toward medial side is called "pronation". When hardness of the EVA sponge is small as mentioned above, the pronation is accelerated. An excessive movement of pronation or a movement of pronation for a long time is called an over-pronation, and generally this over-pronation is not desirable.
A sole for restraining the pronation was developed. FIG. 17 is a plan view showing a midsole disclosed in the Japanese Patent Publication (examined) No. 61-7801. FIG. 18 is a side view showing the midsole disclosed in the same patent publication.
As shown in these drawings, in the prior art disclosed in the mentioned patent publication, a pronation restraining member 202 of a larger hardness than that of a midsole body 201 is disposed at a medial side 11 of a rear foot part of a midsole 200. The midsole 200 according to this prior art supports the medial side of the heel of the foot by the pronation restraining member 202 of a larger hardness, and prevents the heel from inclining toward the medial side of the foot.
However, in this prior art, there exists a problem of easily occurring a feeling of unfitness in the foot when hardness of the pronation restraining member 202 is excessively large.
FIG. 19 is a side view showing a shoe disclosed in the Japanese Laid-Open Utility Model Publication (unexamined) No. 3-51005. FIG. 20 is a bottom view of the sole disclosed in the same publication.
As shown in these drawings, in this prior art disclosed in the above publication, a groove 302 is formed substantially all over outer periphery of a rear foot part 301 of the sole 300 and extending almost equally to left and right (almost equally to medial and lateral sides). This groove 302 improves cushioning performance of the rear foot part of the sole 300.
Several other prior arts for improving the cushioning performance of sole by providing a groove extending equally to medial and lateral sides are also disclosed in the Japanese Utility Model Publication (examined) No. 59-11610 and in the Japanese Laid-Open Utility Model Publication (unexamined) No. 62-200904. These prior arts, however, cannot restrain the pronation.